Update Newton solve to take smaller steps when step leads to increased error. Also restructured to re-evaluate the force-velocity multiplier due to changing fiber-length, which enables the muscle-tendon velocity to be fairly distributed between tendon and fiber instead of assuming zero.
Update Newton solve to take smaller steps when step leads to increased error. Also restructured to re-evaluate the force-velocity multiplier due to changing fiber-length, which enables the muscle-tendon velocity to be fairly distributed between tendon and fiber instead of assuming zero.

opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core